The Gene Thieves in Action

Yet another bacteria post … but these tiny unicellular organisms are so amazing! They’re the grave robbers of the micro-world, without moral values or ethics to prevent them from shamelessly collecting DNA from their dead companions.

This original post about antibiotic resistance looked at why antibiotic resistance was so much of an issue and that was because bacteria like to “share” their genes. So if you have one single bacterium that is resistant, that resistance can spread to many neighbouring bacteria, even from different species.

They perform this “sharing” of genes (horizontal gene transfer) in three ways: transformation, transduction and conjugation. Transduction is when the DNA is spread via a virus (bacteriophage) that “hops” between different bacteria and conjugation is effectively bacterial sex, where bacteria in contact with each other mutually transfer their DNA or sections. And transformation is where these gene thieves come in.

 

Transformation involves bacteria using special, micro-thin pilus (plural pili), which is like a tiny tendril, to grab onto pieces of DNA and pull them into the bacterium and incorporate them into its own genetic pool. And why might there be pieces of DNA just lying around? The main answer is that when a bacterium dies, particularly if it lyses (blows up), it can scatter its DNA fragments around in the environment. Neighbouring bacteria will then extend these pili to grab the DNA sections in case they might be useful. And if one of those fragments help it to survive (like an antibiotic resistance gene), then there’s a higher chance that it’ll continue to live and spread that gene to more bacteria.

 

We’ve known about this process since 1951 and how it can occur between bacterial species and its role in antibiotic resistance since 1959, but this year revealed another exciting step. Some scientists published in Nature Microbiology about their latest breakthrough- capturing this process on video. Dyeing some cholera bacteria with green fluorescence allowed the researchers to observe and film the pili action under a microscope. You can check it out here!

The next step is working out how the pili attach to the DNA in the first place, so maybe that’ll be next year’s discovery!

bacteria-harpoon-still
A picture of the two bacteria (green), the right-hand one is extending a pilus to collect stray DNA (red), from ScienceAlert

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